Charge transporting polymers typified by polyvinylcarbazole (PVK) are promising photoconductive materials for use as electrophotographic photoreceptors or, as reported in the proceedings of the 36th Meeting of Applied Physics Related Association, for use as organic electroluminescence device materials. These elements have a charge transporting layer, and well-known materials forming a charge transporting layer include charge transporting polymers typified by PVK and low-molecular disperse systems comprising a low-molecular weight charge transporting material dispersed in a polymer. Organic electroluminescence devices generally has a vacuum deposited layer of a low-molecular weight charge transporting material. Of these materials, the low-molecular disperse systems are predominantly used especially in electrophotographic photoreceptors for their broad choice of material and high functions. While the recent advancement of performance of organic photoreceptors has made them applicable to high-speed copying machines and printers, the-state-of-art organic photoreceptors are not necessarily sufficient in terms of performance when applied to high-speed copying machines or printers. In particular, improvement in durability of organic photoreceptors has been demanded.
One of the factors decisive of the durability of organic photoreceptors is abrasion resistance of a charge transporting layer. Although low-molecular disperse system charge transporting layers, which are used predominantly, have exhibited satisfactory electrical characteristics, they inherently have poor resistance against mechanical abrasion because of the low molecular weight. Further, when applied to electroluminescence devices, the low-molecular charge transporting material tends to melt due to generated Joule's heat and to crystallize, which cause morphologic changes of the film.
On the other hand, charge transporting polymers have been studied with expectation of eliminating the above-mentioned disadvantages. Examples of charge transporting polymers proposed to date include polycarbonate prepared from a specific dihydroxyarylamine and a bischloroformate, disclosed in U.S. Pat. No. 4,806,443; polycarbonate prepared from a specific dihydroxyarylamine and phosgene, disclosed in U.S. Pat. No. 4,806,444; polycarbonate prepared from a bishydroxyalkylarylamine and a bischloroformate or phosgene, disclosed in U.S. Pat. No. 4,801,517; polycarbonate prepared from a specific dihydroxyarylamine or a bishydroxyalkylarylamine and a bischloroformate or polyester prepared from the former monomer and a bisacyl halide, disclosed in U.S. Pat. Nos. 4,937,165 and 4,959,288; polycarbonate or polyester of an arylamine having a specific fluorene skeleton, disclosed in U.S. Pat. No. 5,034,296; polyurethane, disclosed in U.S. Pat. No. 4,983,482; and polyester comprising a specific bisstyrylbisarylamine as a main chain, disclosed in JP-B-59-28903 (the term "JP-B" as used herein means an "examined published Japanese patent application"). Further, JP-A-61-20953, JP-A-1-134456, JP-A-1-134457, JP-A-1-134462, JP-A-4-133065, and JP-A-4-133066 (the term "JP-A" as used herein means an "unexamined published Japanese patent application) propose polymers having as a pendant group a charge transporting substituent, such as a hydrazone residue or a triarylamine residue, and photoreceptors containing the same. In particular, polymers having a tetraarylbenzidine skeleton exhibit high positive hole mobility and have high practical utility as reported in The 6th International Congress on Advances in Non-impact Printing Technologies, 306 (1990).
Although much study is being given to the charge transporting polymers in order to solve the problems associated with the low-molecular disperse systems, the charge transporting polymers now available are not deemed to be satisfactory in terms of mechanical strength, mobility, and stability against repeated use.